Spectral properties of phototherapy for seasonal affective disorder: a meta‐analvsis

Abstract

The general therapeutic effect of light on seasonal affective disorder (SAD) has been widely acknowledged. However, the antidepressant effect of light does not seem to be the same for different spectra of light. In this study, the authors attempted to study the spectral properties of phototherapy for SAD using a meta-analytical procedure. The findings suggested that light of short to medium wavelengths (blue/green/yellow) seem to be essential for the therapeutic effect of light on SAD. Red wavelengths were relatively ineffective. It was then postulated that SAD may be predisposed and/or precipitated by the inefficiency of the S and M cones in the retina. Furthermore, ultraviolet (UV) waves did not seem to be essential for SAD symptom alleviation by artificial light. Therefore, these potentially harmful UV waves should be blocked in any clinical application of phototherapy for SAD.

Light Therapy for Seasonal Affective Disorder with Blue Narrow-Band Light-Emitting Diodes (LEDs)

“…Additional studies showed green fluorescent light to be therapeutically more potent than an equal photon dose of red fluorescent light (Oren et al 1991). A later meta-analysis reported that red wavelengths are relatively ineffective in the treatment of SAD while short and medium wavelengths of visible light produced antidepressant effects (Lee et al 1997). In some of the studies reviewed, however, red light was studied at dimmer intensities than was light of other wavelengths.…”

Melanopsin Polymorphisms in Seasonal Affective Disorder

“…However, other researchers have found that morning light is comparable in efficacy to evening light or to dual morning-evening administration, replicating the findings of the skeleton photoperiod study (Lee et al, 1997). Lee et al's (1997) …”

“…Light may be antidepressant in SAD independent of its impact on circadian rhythms. Because light has a variety of effects on the body, researchers have attempted to manipulate several light-related parameters with the aim of alleviating SAD, such as timing, intensity, and wavelength (Lee, Chan, Paterson, Janzen, & Blashko, 1997;Oren et al, 1991). Research using bright light therapy to shorten the nocturnal duration of melatonin release, to simulate a summer-like photoperiod, to phaseadvance circadian rhythms and to increase the number of photons delivered to the retina is described below.…”

“…The most potent wavelength for mediation of light-induced melatonin suppression is between 446-477 nm (Brainard et al, 2001). Light therapy using short to medium wavelengths (i.e., 420-580 nm such as blue, green, and yellow light) is more beneficial than longer wavelengths (i.e., red light) to individuals with SAD (Lee et al, 1997). The most effective wavelength for inducing circadian responses in Seasonal Affective Disorder and Melanopsin rodents is similar to that absorbed by the opsins, including melanopsin, rather than other types of light-sensitive molecules such as cryptochromes (Provencio et al, 2000).…”

The Influence of Light Exposure and Seasonal Changes on Short-Term and Longer-Term Changes in Axial Length of the Human Eye

“…Several animal studies have shown that the spectral composition of ambient lighting can influence the course of refractive development (Rohrer et al, 1992;Seidemann & Schaeffel, 2002;Rucker, 2013;Smith et al, 2015), and exposure to different wavelengths of light are also known to influence diurnal rhythms (Lee et al, 1997;Warman et al, 2003;Glickman et al, 2006). This suggests that the spectral content of In Chapter 2, objective light exposure data from young adults and children were acquired with a wrist-worn light sensor over a continuous 14-day period, and a detailed analysis examining the effects of sampling strategies upon metrics describing daily patterns of light exposure was conducted.…”